Compositions comprising base-reactive component and processes for photolithography

ABSTRACT

New photoresist compositions are provided that are useful for immersion lithography. Preferred photoresist compositions of the invention comprise one or more materials that comprise one or more base reactive groups and (i) one or more polar groups distinct from the base reactive groups, and/or (ii) at least one of the base reactive groups is a non-perfluorinated base reactive group. Particularly preferred photoresists of the invention can exhibit reduced leaching of resist materials into an immersion fluid contacting the resist layer during immersion lithography processing.

This application claims the benefit of priority under 35 U.S.C. § 119(e)to U.S. Provisional Application No. 61/413,835, filed Nov. 15, 2010, theentire contents of which application are incorporated herein byreference.

The present invention relates to new photoresist compositions that areparticularly useful in immersion lithography processes. Preferredphotoresist compositions of the invention comprise one or more materialsthat have base-reactive groups, i.e. functional groups that can undergocleavage reactions in the presence of aqueous alkaline photoresistdevelopment during a resist development step.

Photoresists are photosensitive films used for transfer of an image to asubstrate. A coating layer of a photoresist is formed on a substrate andthe photoresist layer is then exposed through a photomask to a source ofactivating radiation. The photomask has areas that are opaque toactivating radiation and other areas that are transparent to activatingradiation. Exposure to activating radiation provides a photoinducedchemical transformation of the photoresist coating to thereby transferthe pattern of the photomask to the photoresist coated substrate.Following exposure, the photoresist is developed to provide a reliefimage that permits selective processing of a substrate. See U.S. PatentApplication Publications 2006/0246373 and 2009/0197204.

The growth of the semiconductor industry is driven by Moore's law whichstates that the complexity of an IC device doubles on average every twoyears. This necessitates the need to lithographically transfer patternsand structures with ever decreasing feature size.

While currently available photoresists are suitable for manyapplications, current resists also can exhibit significant shortcomings,particularly in high performance applications.

For instance, many photoresists will give rise to post-developmentdefects known as “Blob Defects” where fragments of the photoresistmaterial remain in substrate areas that are desired to be cleared upondevelopment (i.e. in the case of a positive resist, exposed resistregions). Such photoresist fragments can interfere with subsequentlithographic processing e.g. etching, ion implantation, and the like.See, for instance, U.S. Pat. No. 6,420,101. See also U.S. 2006/0246373;U.S. 20090197204; U.S. 20090311627; and U.S. provisional application No.61/285,754.

It thus would be desirable to have new photoresists, includingphotoresists that exhibit reduced defects such as Blob Defects.

We now provide new photoresist compositions and processes. Photoresistcompositions comprise a material that comprise one or more base-reactivegroups.

More particularly, preferred photoresists of the invention may comprise:

(i) one or more resins,

(ii) a photoactive component which may suitably comprise one or morephotoacid generator compounds, and

(iii) one or more materials that comprise one or more base-reactivegroups, where the base-reactive groups are reactive after exposure andpost-exposure lithographic processing steps. Preferably, thebase-reactive group(s) will react upon treatment with aqueous alkalinedeveloper compositions, such as 0.26N tetramethylammonium hydroxideaqueous developer compositions. Preferably, such materials that comprisebase-reactive group(s) are substantially non-mixable with the one ormore resins.

In one aspect, preferred base reactive materials will comprise multiplepolar groups, wherein at least one of the multiple polar groups is abase reactive group and at least of the multiple polar groups may be notbase reactive (i.e. not undergo bond cleavage reaction in the presenceof base, such as an acid (e.g. carboxy (—COOK); sulfonic acid (—SO3H),hydroxy (—OH), a halogen particularly other than fluoro such as Br, Clor I; cyano; nitro; sulfono; sulfoxide; esters and acetal groupsincluding photoacid-labile ester and acetal groups; and the like.

More particularly, in one embodiment of this aspect of the invention,preferred base reactive materials may comprise (i) one or more basereactive groups and (ii) one or more acid groups such as one or morecarboxylic acid (—COOH) groups, one or more sulfonic acid (—SO₃H) groupsor other acid groups, or other polar groups such as hydroxy (—OH), ahalogen particularly other than fluoro such as Br, Cl or I; cyano;nitro; sulfono; sulfoxide; and the like. In the case where thebase-reactive material is a polymer, suitably a base reactive moiety andthe further polar group that is not base reactive may be present on thesame polymer repeat unit (e.g. both groups may be present on a singlemonomer that is polymerized to form the base reactive resin), or the abase reactive moiety and the further polar group that is not basereactive may be present on distinct polymer repeat units (e.g. thedistinct groups may be present on distinct monomers that are polymerizedto form the resin).

In a further embodiment of this aspect of the invention, preferred basereactive materials may comprise (i) one or more base reactive groups and(ii) one or more acid-labile groups such as one or more photoacid-labileester moieties (e.g. t-butyl ester) or photoacid-labile acetal groups.In the case where the base-reactive material is a polymer, suitably abase reactive moiety and the photoacid-abile groups may be present onthe same polymer repeat unit (e.g. both groups may be present on asingle monomer that is polymerized to form the base reactive resin), orthe a base reactive moiety and the photoacid-labile may be present ondistinct polymer repeat units (e.g. the distinct groups may be presenton distinct monomers that are polymerized to form the resin).

In another aspect of the invention, preferred base reactive materialswill comprise at least one fluorinated base reactive group, but wherethat group is not perfluorinated. More particularly, such base reactivegroups will comprise both (i) one or more carbon atoms withfluoro-substitution and (ii) one or more carbon atoms that do notcontain fluoro-substitution and suitably are free of otherelectrowithdrawing atoms such as other halo (Cl, Br), nitro, cyano andthe like. Preferably, a fluorinated portion of the base-reactive groupwill be a cleavage product of the base reactive group upon reaction withbase, particularly aqueous alkaline developer.

As referred to herein, a base-reactive group will not reactsignificantly (e.g. will not undergo a bond-breaking reaction) prior toa development step of the photoresist that comprises the base-reactivegroup. Thus, for instance, a base-reactive group will be substantiallyinert during pre-exposure soft-bake, exposure and post-exposure bakesteps. A base-reactive group as referred to herein will typically bereactive under typical photoresist development condition, e.g. singlepuddle development with 0.26N tetrabutyl ammonium hydroxide developercomposition.

Particularly preferred photoresists of the invention can exhibit reduceddefects associated with a resist relief image formed from thephotoresist composition.

While not being bound by any theory, it is believed that photoresists ofthe invention can exhibit reduced defects by providing a morehydrophilic surface of the photoresist relief image as a result ofreaction of the base-reactive groups and production of more polar(hydrophilic) groups during the development step. By providing a morehydrophilic surface, water bead formation on and around the resistrelief image will be diminished during development and subsequentdeionized rinse steps. Reduced water bead formation in turn can resultin reduced occurrence of defects, including Blob Defects where resistfragments may be collected within water beads and deposited in undesiredlocations such as substrate areas bared upon development.

In this regard, particularly preferred photoresists of the inventionafter development will exhibit (coating layers of the resist) watercontact receding angles of less than about 40°, more preferably lessthan 30°, still more preferably less than 25° or 20°. As referred toherein, water contact angles, including receding angles, are as definedand can be determined by procedures as disclosed in Burnett et al., J.Vac. Sci. Techn. B, 23(6), pages 2721-2727 (November/December 2005).

As referred to herein, one or more materials that are substantiallynon-mixable with the one or more photoresist resins can be any materialadded to a photoresist that results in reduced defects upon aqueousalkaline development.

Suitable substantially non-mixable materials for use in photoresists ofthe invention include compositions that comprise silicon and/or fluorinesubstitution in addition to comprising one or more base-reactive groups.

Also preferred are those substantially non-mixable materials thatcontain photoacid-labile groups, such as photoacid-labile ester oracetal groups, including such groups as described herein employed in aresin component of a chemically amplified photoresist.

Preferred substantially non-mixable materials for use in photoresists ofthe invention also will be soluble in the same organic solvent(s) usedto formulate the photoresist composition.

Particularly preferred substantially non-mixable materials for use inphotoresists of the invention also will have lower surface energy and/orsmaller hydrodynamic volume than the one or more resins of thephotoresist's resin component. The lower surface energy can facilitatesegregation or migration of the substantially non-mixable materials totop or upper portions of an applied the photoresist coating layer.Additionally, relative smaller higher hydrodynamic volume also can bepreferred because it can facilitate efficient migration (higherdiffusion coefficient) of the one or more substantially non-mixablematerials to upper regions of the applied photoresist coating layer.

Preferred substantially non-mixable materials for use in photoresists ofthe invention also will be soluble in photoresist developer compositions(e.g. 0.26N aqueous alkaline solution). Thus, in addition tophotoacid-labile groups as discussed above, other aqueousbase-solubilizing groups may be included in the substantiallynon-mixable materials such as hydroxyl, fluoroalcohol (e.g.—C(OH)(CF₃)₂), carboxy and the like.

Suitable substantially non-mixable materials for use in photoresists ofthe invention also may be in the form of particles. Such particles mayinclude polymers that are polymerized in the form discrete particles,i.e. as separate and distinct polymer particles. Such polymer particlestypically have one or more different characteristics from linear orladder polymers such as linear or ladder silicon polymers. For example,such polymer particles may have a defined size and a low molecularweight distribution. More particularly, in a preferred aspect, aplurality of the polymer particles may be employed in a photoresist ofthe invention with a mean particle size (dimension) of from about 5 to3000 angstroms, more preferably from about 5 to 2000 angstroms, stillmore preferably from about 5 to about 1000 angstroms, yet morepreferably from about 10 to about 500 angstroms, even more preferablyfrom 10 to 50 or 200 angstroms. For many applications, particularlypreferred particles have a mean particle size of less than about 200 or100 angstroms.

Additional suitable substantially non-mixable materials for use inphotoresists of the invention may have Si content, includingsilsesquioxane materials, materials with SiO₂ groups, and the like.Preferred silicon-containing substantially non-mixable materials alsoinclude polyhedral oligomeric silsesquioxanxes.

Preferred imaging wavelengths of lithographic systems of the inventioninclude sub-300 nm wavelengths e.g. 248 nm, and sub-200 nm wavelengthse.g. 193 nm. In addition to one or more substantially non-mixablematerials, particularly preferred photoresists of the invention maycontain a photoactive component (e.g. one or more photoacid generatorcompounds) and one or more resins that are chosen from among:

1) a phenolic resin that contains acid-labile groups that can provide achemically amplified positive resist particularly suitable for imagingat 248 nm. Particularly preferred resins of this class include: i)polymers that contain polymerized units of a vinyl phenol and an alkylacrylate, where the polymerized alkyl acrylate units can undergo adeblocking reaction in the presence of photoacid. Exemplary alkylacrylates that can undergo a photoacid-induced deblocking reactioninclude e.g. t-butyl acrylate, t-butyl methacrylate, methyladamantylacrylate, methyl adamantyl methacrylate, and other non-cyclic alkyl andalicyclic acrylates that can undergo a photoacid-induced reaction, suchas polymers in U.S. Pat. Nos. 6,042,997 and 5,492,793, incorporatedherein by reference; ii) polymers that contain polymerized units of avinyl phenol, an optionally substituted vinyl phenyl (e.g. styrene) thatdoes not contain a hydroxy or carboxy ring substituent, and an alkylacrylate such as those deblocking groups described with polymers i)above, such as polymers described in U.S. Pat. No. 6,042,997,incorporated herein by reference; and iii) polymers that contain repeatunits that comprise an acetal or ketal moiety that will react withphotoacid, and optionally aromatic repeat units such as phenyl orphenolic groups; such polymers have been described in U.S. Pat. Nos.5,929,176 and 6,090,526, incorporated herein by reference, as well asblends of i) and/or ii) and/or iii);

2) phenolic resins that do not contain acid-labile groups such aspoly(vinylphenol) and novolak resins that may be employed in I-line andG-line photoresists together with a diazonaphthoquinone photoactivecompound and have been described e.g. in U.S. Pat. Nos. 4,983,492;5,130,410; 5,216,111; and 5529880;

3) a resin that is substantially or completely free of phenyl or otheraromatic groups that can provide a chemically amplified positive resistparticularly suitable for imaging at sub-200 nm wavelengths such as 193nm. Particularly preferred resins of this class include: i) polymersthat contain polymerized units of a non-aromatic cyclic olefin(endocyclic double bond) such as an optionally substituted norbornene,such as polymers described in U.S. Pat. Nos. 5,843,624, and 6,048,664,incorporated herein by reference; ii) polymers that contain alkylacrylate units such as e.g. t-butyl acrylate, t-butyl methacrylate,methyladamantyl acrylate, methyl adamantyl methacrylate, and othernon-cyclic alkyl and alicyclic acrylates; such polymers have beendescribed in U.S. Pat. No. 6,057,083; European Published ApplicationsEP01008913A1 and EP00930542A1; and U.S. Pat. No. 6,136,501, allincorporated herein by reference, and iii) polymers that containpolymerized anhydride units, particularly polymerized maleic anhydrideand/or itaconic anhydride units, such as disclosed in European PublishedApplication EP01008913A1 and U.S. Pat. No. 6,048,662, both incorporatedherein by reference, as well as blends of i) and/or ii) and/or iii);

4) a resin that contains repeat units that contain a hetero atom,particularly oxygen and/or sulfur (but other than an anhydride, i.e. theunit does not contain a keto ring atom), and preferable aresubstantially or completely free of any aromatic units. Preferably, theheteroalicyclic unit is fused to the resin backbone, and furtherpreferred is where the resin comprises a fused carbon alicyclic unitsuch as provided by polymerization of a norborene group and/or ananhydride unit such as provided by polymerization of a maleic anhydrideor itaconic anhydride. Such resins are disclosed in PCT/US01/14914 andU.S. Pat. No. 6,306,554.

5) resins that contain Si-substitution including poly(silsequioxanes)and the like and may be used with an undercoated layer. Such resins aredisclosed e.g. in U.S. Pat. No. 6,803,171.

6) a resin that contains fluorine substitution (fluoropolymer), e.g. asmay be provided by polymerization of tetrafluoroethylene, a fluorinatedaromatic group such as fluoro-styrene compound, compounds that comprisea hexafluoroalcohol moiety, and the like. Examples of such resins aredisclosed e.g. in PCT/US99/21912.

Preferred photoresists of the invention include bothchemically-amplified positive-acting and negative-acting photoresists.Typically preferred chemically-amplified positive resists include one ormore resins that comprise photoacid-labile groups such asphotoacid-labile ester or acetal groups.

The invention further provides methods for forming a photoresist reliefimage and producing an electronic device using photoresists of theinvention. The invention also provides novel articles of manufacturecomprising substrates coated with a photoresist composition of theinvention.

Other aspects of the invention are disclosed infra.

As discussed above, particularly preferred photoresists of the inventioncan exhibit reduced defects following aqueous alkaline development.

As discussed, particularly preferred photoresists of the invention afterdevelopment will have exhibit (coating layers of the resist) watercontact receding angles of less than about 40°, more preferably lessthan 30°, still more preferably less than 25° or 20°. In certain aspectsof the invention, prior to development (including after exposure) aphotoresist composition coating layer of the invention may exhibit awater contact receding angle of in excess of 30°, such as 40° or great,50° or greater, or even 60° or greater.

In preferred photoresists of the invention, upon treatment with aqueousalkaline developer composition (e.g. 0.26N tetramethylammonium hydroxidesingle puddle mode), the water contact receding angle of the photoresistcomposition coating layer will decrease by at least 10, 15, 20, 30, 50,60, 70 or 80 percent.

For photoresist compositions of the invention, preferred materials thatcomprise one or base-reactive groups are resins that comprise one ormore repeat units that comprise base-reactive group(s). Such resins maycontain a wide range of base-reactive groups, e.g. from about 1 to 90percent of the total number of repeat units of a resin may comprisebase-reactive groups, more typically from about 1 to up to about 20, 30,40, 50 or 60 percent of the total number of repeat units of a resin maycomprise base-reactive groups.

Preferred base-reactive groups of a component of resists of theinvention may provide upon treatment with base (such as aqueous alkalinedeveloper) one or more hydroxy groups, one or more carboxylic acidgroups, one or more sulfonic acid groups, and/or one or more other polargroups that will render the resist coating layer more hydrophilic.

More particularly, preferred base-reactive groups and monomers thatcomprise such groups include the following. As should be understood,such monomer can be polymerized to provide a resin that comprisesbase-soluble groups. As discussed above, in the below structures, themonomer with base-reactive group is depicted on the left and the monomerafter reaction with base (e.g. to provide a hydroxyl group) is depictedin the right.

Single Hydroxy Group

Preferred base-reactive groups include those moieties that may provide asingle hydroxyl group upon treatment with base (such as aqueous alkalinedeveloper composition). More specifically, suitable monomers thatcomprise such base-reactive groups include those of the followingFormula (I):

where M is a polymerizable functional group including vinyl and acrylic,R an alkyl spacer group (e.g. C₁₋₂₀ linear, branched or cyclic) with orwithout carboxyl linkages, Rf a fluoro or perfluoro alkyl groups (e.g.C₁₋₂₀ alkyl with 1 to 8 fluoro atoms) with at least the alfa carbon (thecarbon next to the carbonyl carbon) being fluorinated.

Exemplary monomers of the above Formula (I) include the followingMonomers 1 through 6. As discussed above, in the below structures, themonomer with base-reactive group is depicted on the left and the monomerafter reaction with base to provide a hydroxyl group is depicted in theright.

Multiple Hydroxy Groups

Additional preferred base-reactive groups include those moieties thatmay provide multiple hydroxyl group upon treatment with base (such asaqueous alkaline developer composition). More specifically, suitablemonomers that comprise such base-reactive groups include those of thefollowing Formula (II):

where M is a polymerizable functional group including vinyl and acrylic,R an alkyl spacer group (e.g. C₁₋₂₀ linear, branched or cyclic) with orwithout carboxyl linkages, Rf a fluoro or perfluoro alkyl groups (e.g.C₁₋₂₀ alkyl with 1 to 8 fluoro atoms) with at least the alfa carbon (thecarbon next to the carbonyl carbon) being fluorinated, and n being aninteger equal to or greater than 2.

Exemplary monomers of the above Formula (II) include the followingMonomers 7 through 9. In the below structures, the monomer withbase-reactive group is depicted on the left and the monomer afterreaction with base to provide a hydroxyl group is depicted in the right.

Switching to Carboxylic Acid Group

Additional preferred base-reactive groups include those moieties thatmay provide one or more carboxylic acid groups upon treatment with base(such as aqueous alkaline developer composition). More specifically,suitable monomers that comprise such base-reactive groups include thoseof the following Formula (III):

where M is a polymerizable functional group including vinyl and acrylic,R1 an alkyl spacer group (e.g. C₁₋₂₀ linear, branched or cyclic) with orwithout carboxyl linkages, Rf a fluoro or perfluoro alkylene groups(e.g. C₁₋₂₀ alkyl with 1 too 8 fluoro atoms) with at least the alfacarbon (the carbon next to the carbonyl carbon) being fluorinated, andR2 an alkyl group (e.g. C₁₋₂₀ linear, branched or cyclic).

Exemplary monomers of the above Formula (III) include the followingMonomers 10 and 11. In the below structures, the monomer withbase-reactive group is depicted on the left and the monomer afterreaction with base to provide a hydroxyl group is depicted in the right.

As discussed above, suitable materials of photoresists of the inventionthat are substantially non-mixable with the resist resin component canbe readily identified by simple testing. In particular, as referred toherein, preferred substantially non-mixable materials will provide adecreased occurrence or amount of defects upon aqueous alkalinedevelopment relative to a comparable photoresist relative to the samephotoresist system that is processed into the same manner, but in theabsence of the candidate substantially non-mixable material(s).Assessment of defects (or absence thereof) can be made via scanningelectron micrography. Detection of photoresist material in the immersionfluid can be conducted as described in Example 2 of U.S. PatentPublication 2006/0246373 and includes mass spectroscopy analysis of theimmersion fluid before and after exposure to the photoresist. In suchanalysis, the immersion fluid directly contacts the tested photoresistcomposition layer for about 60 seconds during exposure. Preferably,addition of one or more substantially non-mixable materials provides atleast a 10 percent reduction in photoresist material (again, acid ororganics as detected by mass spectroscopy) residing in the immersionfluid relative to the same photoresist that does not employ suchsubstantially non-mixable material(s), more preferably the one or moresubstantially non-mixable materials provides at least a 20, 50, or 100,200, 500, or 1000 percent reduction photoresist material (again, acidand/or organics) residing in to the immersion fluid relative to the samephotoresist that does not contain the substantially non-mixablematerial(s).

Particularly preferred substantially non-mixable materials includehigher order polymers e.g. copolymers, terpolymers, tetrapolymers andpentapolymers. Particularly preferred are such polymers that comprisefluorine substitution in addition to carboxy substitution. Preferredfluoro substitution include perfluoro groups e.g. F₃C—, F₃CCF₂—, andfluorinated alcohols e.g. (F₃C)₂C(OH)—.

As discussed above, suitable substantially non-mixable materials includeSi-containing materials. Especially preferred substantially non-mixablematerials include nanostructured compositions, which are commerciallyavailable from groups such as Hybrid Plastics (Fountain Valley, Calif.),Sigma/Aldrich, and others. Such materials may include molecular silicaswhich have a Si—O core enveloped by organic groups; silanols; andpolymers and resins which include silsesquioxane cage-structuredcompounds and may be silicones, styrenics, acrylics, alicyclics such asnorbornenes and others.

Particles (including organic particles) useful as substantiallynon-mixable materials include Si-containing and fluorinated materialsthat have carboxy substitution. Such particles are commerciallyavailable, or can be readily synthesized, e.g. by reaction of one ormore monomers together with a crosslinking agent and an initiatorcompound if desired. The reacted monomers may have substitution asdesired e.g. fluorine, Si groups, photoacid-labile groups such asphotoacid-labile esters or acetals, other base-solubilizing groups suchas alcohols and the like. See Example 1 of U.S. Patent Publication2006/0246373 for an exemplary synthesis of such particles produced withmultiple distinct monomers, where one of the monomers provides aphotoacid-labile group to the resulting polymer particle.

The substantially non-mixable material(s) may be present in aphotoresist composition in relatively small amounts and still provideeffective results. For instance, the one or more substantiallynon-mixable materials may be suitable present in about 0.1 to 20 weightpercent based on total weight of a fluid photoresist composition.Suitable amounts also are provided in the examples which follow.

As discussed above, preferred photoresists for use in accordance withthe invention include positive-acting or negative-acting chemicallyamplified photoresists, i.e. negative-acting resist compositions whichundergo a photoacid-promoted crosslinking reaction to render exposedregions of a coating layer of the resist less developer soluble thanunexposed regions, and positive-acting resist compositions which undergoa photoacid-promoted deprotection reaction of acid labile groups of oneor more composition components to render exposed regions of a coatinglayer of the resist more soluble in an aqueous developer than unexposedregions. Ester groups that contain a tertiary non-cyclic alkyl carbon(e.g. t-butyl) or a tertiary alicyclic carbon (e.g. methyladamantyl)covalently linked to the carboxyloxygen of the ester are often preferredphotoacid-labile groups of resins employed in photoresists of theinvention. Acetal photoacid-labile groups also will be preferred.

Preferred photoresists of the invention typically comprise a resincomponent and a photoactive component. Preferably the resin hasfunctional groups that impart alkaline aqueous developability to theresist composition. For example, preferred are resin binders thatcomprise polar functional groups such as hydroxyl or carboxylate.Preferably a resin component is used in a resist composition in anamount sufficient to render the resist developable with an aqueousalkaline solution.

For imaging at wavelengths greater than 200 nm, such as 248 nm, phenolicresins are typically preferred. Preferred phenolic resins are poly(vinylphenols) which may be formed by block polymerization, emulsionpolymerization or solution polymerization of the corresponding monomersin the presence of a catalyst. Vinylphenols useful for the production ofpolyvinyl phenol resins may be prepared, for example, by hydrolysis ofcommercially available coumarin or substituted coumarin, followed bydecarboxylation of the resulting hydroxy cinnamic acids. Usefulvinylphenols may also be prepared by dehydration of the correspondinghydroxy alkyl phenols or by decarboxylation of hydroxy cinnamic acidsresulting from the reaction of substituted or nonsubstitutedhydroxybenzaldehydes with malonic acid. Preferred polyvinylphenol resinsprepared from such vinylphenols have a molecular weight range of fromabout 2,000 to about 60,000 daltons.

Also preferred for imaging at wavelengths greater than 200 nm, such as248 nm are chemically amplified photoresists that comprise in admixturea photoactive component and a resin component that comprises a copolymercontaining both phenolic and non-phenolic units. For example, onepreferred group of such copolymers has acid labile groups substantially,essentially or completely only on non-phenolic units of the copolymer,particularly alkylacrylate photoacid-labile groups, i.e. aphenolic-alkyl acrylate copolymer. One especially preferred copolymerbinder has repeating units x and y of the following formula:

wherein the hydroxyl group be present at either the ortho, meta or parapositions throughout the copolymer, and R′ is substituted orunsubstituted alkyl having 1 to about 18 carbon atoms, more typically 1to about 6 to 8 carbon atoms. Tert-butyl is a generally preferred R′group. An R′ group may be optionally substituted by e.g. one or morehalogen (particularly F, Cl or Br), C₁₋₈ alkoxy, C₂₋₈ alkenyl, etc. Theunits x and y may be regularly alternating in the copolymer, or may berandomly interspersed through the polymer. Such copolymers can bereadily formed. For example, for resins of the above formula, vinylphenols and a substituted or unsubstituted alkyl acrylate such ast-butylacrylate and the like may be condensed under free radicalconditions as known in the art. The substituted ester moiety, i.e.R′—O—C(═O)—, moiety of the acrylate units serves as the acid labilegroups of the resin and will undergo photoacid induced cleavage uponexposure of a coating layer of a photoresist containing the resin.Preferably the copolymer will have a M_(w) of from about 8,000 to about50,000, more preferably about 15,000 to about 30,000 with a molecularweight distribution of about 3 or less, more preferably a molecularweight distribution of about 2 or less. Non-phenolic resins, e.g. acopolymer of an alkyl acrylate such as t-butylacrylate ort-butylmethacrylate and a vinyl alicyclic such as a vinyl norbornanyl orvinyl cyclohexanol compound, also may be used as a resin binder incompositions of the invention. Such copolymers also may be prepared bysuch free radical polymerization or other known procedures and suitablywill have a M_(w) of from about 8,000 to about 50,000, and a molecularweight distribution of about 3 or less.

Other preferred resins that have acid-labile deblocking groups for usein a positive-acting chemically-amplified photoresist of the inventionhave been disclosed in European Patent Application 0829766A2 of theShipley Company (resins with acetal and ketal resins) and EuropeanPatent Application EP0783136A2 of the Shipley Company (terpolymers andother copolymers including units of 1) styrene; 2) hydroxystyrene; and3) acid labile groups, particularly alkyl acrylate acid labile groupssuch as t-butylacrylate or t-butylmethacrylate). In general, resinshaving a variety of acid labile groups will be suitable, such as acidsensitive esters, carbonates, ethers, imides, etc. The photoacid labilegroups will more typically be pendant from a polymer backbone, althoughresins that have acid labile groups that are integral to the polymerbackbone also may be employed.

As discussed above, for imaging at sub-200 nm wavelengths such as 193nm, preferably a photoresist is employed that contains one or morepolymers that are substantially, essentially or completely free ofphenyl or other aromatic groups. For example, for sub-200 nm imaging,preferred photoresist polymers contain less than about 5 mole percentaromatic groups, more preferably less than about 1 or 2 mole percentaromatic groups, more preferably less than about 0.1, 0.02, 0.04 and0.08 mole percent aromatic groups and still more preferably less thanabout 0.01 mole percent aromatic groups. Particularly preferred polymersare completely free of aromatic groups. Aromatic groups can be highlyabsorbing of sub-200 nm radiation and thus are undesirable for polymersused in photoresists imaged with such short wavelength radiation.

Suitable polymers that are substantially or completely free of aromaticgroups and may be formulated with a PAG of the invention to provide aphotoresist for sub-200 nm imaging are disclosed in European applicationEP930542A1 and U.S. Pat. Nos. 6,692,888 and 6,680,159, all of theShipley Company.

Suitable polymers that are substantially or completely free of aromaticgroups suitably contain acrylate units such as photoacid-labile acrylateunits as may be provided by polymerization of methyladamanatylacrylate,methyladamantylmethacrylate, ethylfenchylacrylate,ethylfenchylmethacrylate, and the like; fused non-aromatic alicyclicgroups such as may be provided by polymerization of a norbornenecompound or other alicyclic compound having an endocyclic carbon-carbondouble bond; an anhydride such as may be provided by polymerization ofmaleic anhydride and/or itaconic anhydride; and the like.

Preferred negative-acting compositions of the invention comprise one ormore materials (such as a crosslinker component e.g. an amine-basedmaterials such as a melamine resin) that will cure, crosslink or hardenupon exposure to acid, and a photoactive component of the invention.Particularly preferred negative acting compositions comprise a resinbinder such as a phenolic resin, a crosslinker component and aphotoactive component of the invention. Such compositions and the usethereof has been disclosed in European Patent Applications 0164248 and0232972 and in U.S. Pat. No. 5,128,232 to Thackeray et al. Preferredphenolic resins for use as the resin binder component include novolaksand poly(vinylphenol)s such as those discussed above. Preferredcrosslinkers include amine-based materials, including melamine,glycolurils, benzoguanamine-based materials and urea-based materials.Melamine-formaldehyde resins are generally most preferred. Suchcrosslinkers are commercially available, e.g. the melamine resins soldby American Cyanamid under the trade names Cymel 300, 301 and 303.Glycoluril resins are sold by American Cyanamid under trade names Cymel1170, 1171, 1172, urea-based resins are sold under the trade names ofBeetle 60, 65 and 80, and benzoguanamine resins are sold under the tradenames Cymel 1123 and 1125.

For imaging at sub-200 nm wavelengths such as 193 nm, preferrednegative-acting photoresists are disclosed in WO 03077029 to the ShipleyCompany.

Photoresists of the invention also may contain other materials. Forexample, other optional additives include actinic and contrast dyes,anti-striation agents, plasticizers, speed enhancers, sensitizers (e.g.for use of a PAG of the invention at longer wavelengths such as I-line(i.e. 365 nm) or G-line wavelengths), etc. Such optional additivestypically will be present in minor concentration in a photoresistcomposition except for fillers and dyes which may be present inrelatively large concentrations such as, e.g., in amounts of from 5 to30 percent by weight of the total weight of a resist's dry components.

A preferred optional additive of resists of the invention is an addedbase, e.g. a caprolactam, which can enhance resolution of a developedresist relief image. The added base is suitably used in relatively smallamounts, e.g. about 1 to 10 percent by weight relative to the PAG, moretypically 1 to about 5 weight percent. Other suitable basic additivesinclude ammonium sulfonate salts such as piperidinium p-toluenesulfonateand dicyclohexylammonium p-toluenesulfonate; alkyl amines such astripropylamine and dodecylamine; aryl amines such as diphenylamine,triphenylamine, aminophenol,2-(4-aminophenyl)-2-(4-hydroxyphenyl)propane, etc.

The resin component of resists of the invention is typically used in anamount sufficient to render an exposed coating layer of the resistdevelopable such as with an aqueous alkaline solution. Moreparticularly, a resin binder will suitably comprise 50 to about 90weight percent of total solids of the resist. The photoactive componentshould be present in an amount sufficient to enable generation of alatent image in a coating layer of the resist. More specifically, thephotoactive component will suitably be present in an amount of fromabout 1 to 40 weight percent of total solids of a resist. Typically,lesser amounts of the photoactive component will be suitable forchemically amplified resists.

Photoresists for use in the invention also comprise a photoacidgenerator (i.e. “PAG”) that is suitably employed in an amount sufficientto generate a latent image in a coating layer of the resist uponexposure to activating radiation. Preferred PAGs for imaging at 193 nmand 248 nm imaging include imidosulfonates such as compounds of thefollowing formula:

wherein R is camphor, adamantane, alkyl (e.g. C₁₋₁₂ alkyl) andfluoroalkyl such as fluoro(C₁₋₁₈alkyl) e.g. RCF₂— where R is optionallysubstituted adamantyl.

Also preferred is a triphenyl sulfonium PAG, complexed with anions suchas the sulfonate anions mentioned above, particularly a perfluoroalkylsulfonate such as perfluorobutane sulfonate.

Other known PAGS also may be employed in the resists of the invention.Particularly for 193 nm imaging, generally preferred are PAGS that donot contain aromatic groups, such as the above-mentionedimidosulfonates, in order to provide enhanced transparency.

Other suitable photoacid generators for use in present photoresistsinclude for example: onium salts, for example, triphenylsulfoniumtrifluoromethanesulfonate, (p-tert-butoxyphenyl)diphenylsulfoniumtrifluoromethanesulfonate, tris(p-tert-butoxyphenyl)sulfoniumtrifluoromethanesulfonate, triphenylsulfonium p-toluenesulfonate,nitrobenzyl derivatives, for example, 2-nitrobenzyl p-toluenesulfonate,2,6-dinitrobenzyl p-toluenesulfonate, and 2,4-dinitrobenzylp-toluenesulfonate; sulfonic acid esters, for example,1,2,3-tris(methanesulfonyloxy)benzene,1,2,3-tris(trifluoromethanesulfonyloxy)benzene, and1,2,3-tris(p-toluenesulfonyloxy)benzene; diazomethane derivatives, forexample, bis(benzenesulfonyl)diazomethane,bis(p-toluenesulfonyl)diazomethane; glyoxime derivatives, for example,bis-O-(p-toluenensulfonyl)-α-dimethylglyoxime, andbis-O-(n-butanesulfonyl)-α-dimethylglyoxime; sulfonic acid esterderivatives of an N-hydroxyimide compound, for example,N-hydroxysuccinimide methanesulfonic acid ester, N-hydroxysuccinimidetrifluoromethanesulfonic acid ester; and halogen-containing triazinecompounds, for example,2-(4-methoxyphenyl)-4,6-bis(trichloromethyl)-1,3,5-triazine, and2-(4-methoxynaphthyl)-4,6-bis(trichloromethyl)-1,3,5-triazine. One ormore of such PAGs can be used.

A preferred optional additive of photoresist used in accordance with theinvention is an added base, particularly tetramethylammonium hydroxide(TBAH), or tetramethylammonium lactate, which can enhance resolution ofa developed resist relief image. For resists imaged at 193 nm, apreferred added base is a lactate salt of tetramethylammonium hydroxideas well as various other amines such as triisopropanol, diazabicycloundecene or diazabicyclononene. The added base is suitably used inrelatively small amounts, e.g. about 0.03 to 5 percent by weightrelative to the total solids.

Photoresists used in accordance with the invention also may containother optional materials. For example, other optional additives includeanti-striation agents, plasticizers, speed enhancers, etc. Such optionaladditives typically will be present in minor concentrations in aphotoresist composition except for fillers and dyes which may be presentin relatively large concentrations, e.g., in amounts of from about 5 to30 percent by weight of the total weight of a resist's dry components.

The photoresists used in accordance with the invention are generallyprepared following known procedures. For example, a resist of theinvention can be prepared as a coating composition by dissolving thecomponents of the photoresist in a suitable solvent such as, e.g., aglycol ether such as 2-methoxyethyl ether (diglyme), ethylene glycolmonomethyl ether, propylene glycol monomethyl ether; propylene glycolmonomethyl ether acetate; lactates such as ethyl lactate or methyllactate, with ethyl lactate being preferred; propionates, particularlymethyl propionate, ethyl propionate and ethyl ethoxy propionate; aCellosolve ester such as methyl Cellosolve acetate; an aromatichydrocarbon such toluene or xylene; or a ketone such as methylethylketone, cyclohexanone and 2-heptanone. Typically the solids content ofthe photoresist varies between 5 and 35 percent by weight of the totalweight of the photoresist composition. Blends of such solvents also aresuitable.

Liquid photoresist compositions may be applied to a substrate such as byspinning, dipping, roller coating or other conventional coatingtechnique. When spin coating, the solids content of the coating solutioncan be adjusted to provide a desired film thickness based upon thespecific spinning equipment utilized, the viscosity of the solution, thespeed of the spinner and the amount of time allowed for spinning.

Photoresist compositions used in accordance with the invention aresuitably applied to substrates conventionally used in processesinvolving coating with photoresists. For example, the composition may beapplied over silicon wafers or silicon wafers coated with silicondioxide for the production of microprocessors and other integratedcircuit components. Aluminum-aluminum oxide, gallium arsenide, ceramic,quartz, copper, glass substrates and the like are also suitablyemployed. Photoresists also may be suitably applied over anantireflective layer, particularly an organic antireflective layer.

Following coating of the photoresist onto a surface, it may be dried byheating to remove the solvent until preferably the photoresist coatingis tack free.

The photoresist layer (with overcoated barrier composition layer, ifpresent) in then exposed in an immersion lithography system, i.e. wherethe space between the exposure tool (particularly the projection lens)and the photoresist coated substrate is occupied by an immersion fluid,such as water or water mixed with one or more additives such as cesiumsulfate which can provide a fluid of enhanced refractive index.Preferably the immersion fluid (e.g., water) has been treated to avoidbubbles, e.g. water can be degassed to avoid nanobubbles.

References herein to “immersion exposing” or other similar termindicates that exposure is conducted with such a fluid layer (e.g. wateror water with additives) interposed between an exposure tool and thecoated photoresist composition layer.

The photoresist composition layer is then suitably patterned exposed toactivating radiation with the exposure energy typically ranging fromabout 1 to 100 mJ/cm², dependent upon the exposure tool and thecomponents of the photoresist composition. References herein to exposinga photoresist composition to radiation that is activating for thephotoresist indicates that the radiation is capable of forming a latentimage in the photoresist such as by causing a reaction of thephotoactive component (e.g. producing photoacid from the photoacidgenerator compound).

As discussed above, photoresist compositions are preferablyphotoactivated by a short exposure wavelength, particularly a sub-400nm, sub-300 and sub-200 nm exposure wavelength, with I-line (365 nm),248 nm and 193 nm being particularly preferred exposure wavelengths aswell as EUV.

Following exposure, the film layer of the composition is preferablybaked at temperatures ranging from about 70° C. to about 160° C.Thereafter, the film is developed, preferably by treatment with anaqueous based developer such as quaternary ammonium hydroxide solutionssuch as a tetra-alkyl ammonium hydroxide solution; various aminesolutions preferably a 0.26 N tetramethylammonium hydroxide, such asethyl amine, n-propyl amine, diethyl amine, di-n-propyl amine, triethylamine, or methyldiethyl amine; alcohol amines such as diethanol amine ortriethanol amine; cyclic amines such as pyrrole, pyridine, etc. Ingeneral, development is in accordance with procedures recognized in theart.

Following development of the photoresist coating over the substrate, thedeveloped substrate may be selectively processed on those areas bared ofresist, for example by chemically etching or plating substrate areasbared of resist in accordance with procedures known in the art. For themanufacture of microelectronic substrates, e.g., the manufacture ofsilicon dioxide wafers, suitable etchants include a gas etchant, e.g. ahalogen plasma etchant such as a chlorine or fluorine-based etchant sucha Cl₂ or CF₄/CHF₃ etchant applied as a plasma stream. After suchprocessing, resist may be removed from the processed substrate usingknown stripping procedures.

All documents mentioned herein are incorporated herein by reference. Thefollowing non-limiting examples are illustrative of the invention. Alldocuments mentioned herein are incorporated by reference in theirentirety.

GENERAL COMMENTS TO EXAMPLES

In the following Examples, references to any of Monomers 1 through 11includes the above-designated monomer structures in protected form (i.e.before the structure is shown post-treatment with alkaline developer).

In the following Examples, references to monomers of 2233tMBA, 3,5-HFAand ECPMA designate the following structures:

In the Table in Example 3 below, the water contact angles of ⊖s—staticcontact angle; ⊖r—receding angle; and ⊖a—advancing angle. Those watercontact angles are as defined and can be determined by procedures asdisclosed in Burnett et al., J. Vac. Sci. Techn. B, 23(6), pages2721-2727 (November/December 2005).

Example 1 Monomer Synthesis

Step 1 Component MW(g) grams mmol mol ratio TFPA (2,2,3,3- 146 10 68.501 Tetrafluoropropionic acid) Phosphorus pentoxide 141.94 7.00 49.32 0.72

-   -   1) To a 25 ml 3N—RB flask were added 10 g        2,2,3,3-tetrafluoropropionic acid, together with 5 g phosphorus        pentoxide. Heated up the mixture to reflux for 2 hrs (oil bath        133° C.).    -   2) After checking F-NMR and found 90%+ conversion of acid to        anhydride (anhydride is hydroscopic and react with water in NMR        solvent to give low conversion ratio), cooled down reaction        flask.    -   3) Add another 2 g of phosphorus pentoxide into the mixture,        then use vacuum distillation to collect 54-56° C./28 Torr        fraction, NMR indicated 6.55 g pure product was obtained, with        yield of 63%.

Step 2 Component MW(g) grams mmol mol ratio TFPAA (2,2,3,3- 274.07 6.5521.50 1.1 Tetrafluoropropionic acid anhydride), 90% pure by F-NMR GMA(Glycidyl methacrylate) 142.25 2.78 19.60 1 Cyanox 1790 inhibitor 6990.06 0.009 0.004

-   -   1) To a 25 ml 3N—RB flask were added 6.55 g        2,2,3,3-tetrafluoropropionic acid anhydride, 2.78 g glycidyl        methacrylate, with 30 mg Cyanox 1790 inhibitor.    -   2) The reaction flask was stirred at 80° C. for 2 hrs. After        using H-NMR to detect no GMA peak left, cooled down the reaction        mixtures    -   3) Add another 30 mg Cyanox 1790 inhibitor into the mixture,        directly ran vacuum distillation for purification, collected 7.2        g of the fraction 96-97° C./0.7 Torr.

Example 2 Polymer Synthesis: 94/6 GMA-2233TFP/ECPMA

The following is an example for making a 60 g batch of the titlepolymer.

1). Preparing the Reactor

Charge 30 g of propylene glycol monomethyl ether into a 250 ml-neck,round bottom flask with a magnetic stir bar and a heating controlthermocouple. Bring the solution temperature to 97° C. with stirring.

2). Preparing Monomer/Initiator Solution

To a suitable container, add 56.4 g GMA-2233TFP monomer, 3.6 g ECPMAmonomer and 30 g SURF. Shake the container to mix all components thenplace it in an ice bath.

Weigh 1.8 g initiator (Vazo 67) and add it to the container. Shake thecontainer to dissolve the initiator then place it back to the ice bath.

3). Feeding Monomer/Initiator Solution

Feed the monomer/initiator solution into the reactor with a feeding rateof 250 μl/13 sec (or 19.2 μl/sec)

After feeding, continue to maintain the reactor temp at 97° C. foradditional 2 to 3 hrs, then let the reactor cool naturally to room temp.

Example 3 Photoresist Preparation and Processing

A photoresist composition is prepared by admixing the followingmaterials in the specified amounts:

1. Resin component: Terpolymer of (2-methyl-2-adamantylmethacrylate/beta-hydroxy-gamma-butyrolactonemethacrylate/cyano-norbornyl methacrylate in an amount of 6.79 weight %based on total weight of the photoresist composition;

2. Photoacid generator compound: T-butyl phenyl tetramethylene sulfoniumperfluorobutanesulfonate in an amount of 0.284 weight % based on totalweight of the photoresist composition;

3. Base additive: N-Alkyl Caprolactam in an amount of 0.017 weight %based on total weight of the photoresist composition;

4. Substantially non-mixable additive: Polymer of Example 2 prepared asdescribed in Example 1 above and in an amount of 0.213 weight % based ontotal weight of the photoresist composition.

5. Solvent component: propylene glycol monomethyl ether acetate toprovide about a 90 percent fluid composition.

This photoresist composition is spin-coated onto silicon wafers, driedon vacuum hotplate to remove soft-plate and then exposed in an immersionlithography process with aqueous immersion fluid directly contacting thedried photoresist layers. In that immersion system, the photoresistlayers is exposed to patterned 193 nm radiation at a dose of 24.1mJ/cm².

The photoresist layers is then post-exposed baked (such as at about 120°C.) and developed with 0.26N alkaline aqueous developer solution.

To evaluate leaching of resist components after the post-exposure bakeand before development, the immersion fluid is evaluated for thephotoacid in the resist and its photo-degradation byproducts by LC/massspectroscopy (60 second leaching time tested).

Example 4 Synthesis of Additional Resin Comprising Base Cleavable Groups

A. Monomer and initiator mixture: weigh 7.00 g ofCH₃(CH═CH)C(═O)O(CH₂)₂)O(C═O)CF₃ (the first monomer) and 4.80 g of(CH₂═CH)C(═O)OC(CH(CH₃))₂C(CH₃)₃ (the second monomer), 0.42 g ofTrignox-23 (initiator) and 17.0 g PGMEA (solvent) into a feeding vial.

B. Reactor: 30 g of PGMEA in a reactor and maintain at 85° C.

C. Feed A into B: A is fed into B with a constant feeding rate in 120minutes.

D. Holding temperature: after feeding A into B, the temperature of thereactor is maintained at 85° C. for additional two hrs, then allow thereactor temp to cool down naturally to room temperature.

This resin with base-reactive groups from the reactor can be used in aphotoresist composition without further purification

What is claimed is:
 1. A method for processing a photoresist composition, comprising: a) applying on a substrate a photoresist composition comprising: (i) one or more resins, (ii) a photoactive component, and (iii) one or more materials distinct from the one or more resins and that comprise (A) one or more base reactive groups and (B) one or more nitro or sulfoxide groups that are in addition to and distinct from one or more base reactive groups; wherein the (A) one or more base reactive groups and the (B) nitro or sulfoxide groups are present on the same resin repeat unit, wherein the one or more materials (iii) comprise photoacid-labile groups; and b) immersion exposing the applied photoresist layer to radiation activating for the photoresist composition.
 2. The method of claim 1 wherein the one or more materials (iii) comprise one or more acid groups that are in addition to and distinct from one or more base reactive groups.
 3. The method of claim 1 wherein the one or more materials (iii) comprise one or more photoacid-labile groups that are in addition to and distinct from the one or more base reactive groups.
 4. The method of claim 1 further comprising developing the exposed photoresist layer with aqueous alkaline developer whereby the one or more base-reactive groups undergo a bond-breaking reaction to provide one or more polar groups.
 5. The method of claim 4 wherein the photoresist layer prior to development has a water contact receding angle of in excess of 40°, and the photoresist layer after development has a water contact receding angle of less than 30°.
 6. The method of claim 1 wherein the one or more materials (iii) comprise groups that react with aqueous alkaline developer to provide hydroxyl or sulfonic acid groups.
 7. The method of claim 1 wherein the photoacid-labile groups comprise ester photoacid-labile moieties.
 8. The method of claim 1 wherein one or more base reactive groups are fluorinated.
 9. The method of claim 1 wherein one or more base reactive groups are fluorinated but not perfluorinated.
 10. A method for processing a photoresist composition, comprising: a) applying on a substrate a photoresist composition comprising: (i) one or more resins, (ii) a photoactive component, and (iii) one or more materials distinct from the one or more resins and that comprise one or more base reactive groups derived from the following monomer:

and b) immersion exposing the applied photoresist layer to radiation activating for the photoresist composition.
 11. The method of claim 10 wherein the (iii) one or more materials further comprise photoacid-labile groups.
 12. The method of claim 10 wherein the (iii) one or more materials are resins. 